RNA-binding peptide and endosomal escape-assisting peptide (L2) improved siRNA delivery by the hexahistidine–metal assembly

Small interfering RNAs (siRNAs), comprising 21–23 nucleotides, function by complementary binding to specific mRNA sequences, thereby suppressing target protein expression. Despite their vast potential in disease therapy, siRNAs face challenges due to their susceptibility to degradation and high electronegativity, rendering them unstable in the bloodstream and impeding their passage across endothelial barriers. Moreover, successful intracellular delivery necessitates overcoming endosomal entrapment, posing a significant hurdle for carrier material development. In this study, leveraging the strong affinity of histidine oligomers (His6) for metal ions, we engineered nanoparticles (HmA) by gentle assembly with divalent zinc ions under pH = 8 conditions. We designed the RNA-binding functional peptide L2-NTD to enhance siRNA stability and delivery efficiency when complexed with HmA. The resulting siRNA+L2-NTD@HmA nanoparticles were formed via in situ encapsulation, ensuring efficient siRNA delivery into cells with minimal cytotoxicity and degradation. This approach presents a novel strategy for the design and artificial fabrication of carriers for effective RNA delivery.